Cell Structure

• There are two main types of microscopes: light microscopes and electron microscopes.
• Viruses don't have a cell wall and are reproduced within a host cell, making them unaffected by antibiotics.
• HIV is treated with antiretroviral drugs which keep the levels of HIV in the blood stream very low, reducing the impact on the host's immune system.
• Light microscopes use a pair of convex glass lenses that can resolve images that are 0.2um apart.
• The resolution of a light microscope is restricted to 0.2um due to the wavelength of light.
• Electron microscopes can distinguish between items 0.1nm apart.
• The magnification of an image as seen through a microscope can be calculated using the equation: Magnification = size of image/size of real object.
• Resolution is defined as the minimum distance apart that two objects can be distinguished as separate objects in an image.
• The greater the resolution, the more clear the image will be.
• There are two main types of electron microscope: transmission electron microscopes (TEM) and scanning electron microscopes (SEM).
• Electron microscopes work in a similar way to light microscopes, but instead use a beam of electrons that are focused by electromagnets inside a vacuum environment.
• There are a number of ethical considerations to take into account when looking at vaccines, including production and testing of vaccines may be done on animals, the risks of the vaccine need to be balanced with the benefits, the vaccine must be tested on humans first to determine toxicity, vaccinations are very expensive, and should vaccinations be compulsory or should people be able to opt out of having a vaccination.
• Herd immunity is the concept that if you vaccinate enough people in the population then eventually the pathogen won’t be able to be transmitted from different hosts, protecting those who aren’t vaccinated.
• To identify HIV, an Enzyme Linked Immunosorbent Assay (ELISA) can be used, which detects the presence and quantity of the antigen found on HIV.
• Active immunity results in the creation of memory B cells which will trigger a rapid secondary immune response should the same pathogen ever be detected again.
• The success of a vaccination program is dependent on a number of factors such as cost of the vaccine, severity of the side effects, ease of production, transportation and administration, and number of people who need to be vaccinated for herd immunity.
• Monoclonal antibodies are useful due to their ability to produce many clones of a single type of antibody, and have many different uses including direct therapy, indirect therapy, diagnosis, and pregnancy testing.
• An example of a virus that does this is Influenza, which rapidly changes its antigens and therefore immunity against this virus is only short lived.
• Antibiotics are ineffective against HIV and viruses because many antibiotics work by preventing bacteria from making cells walls, without which the bacterial cell cannot control the entry and exit of water and will therefore burst.
• Vaccines are not always useful in preventing a disease outbreak because the antigen on the surface of the pathogen can change, removing immunity.
• Human immunodeficiency virus (HIV) is a pathogen that can lead to the disease acquired immune deficiency syndrome (AIDS), and has the following structure: a lipid envelope with embedded attachment proteins, inside a protein capsid where the genetic material (RNA) and reverse transcriptase enzymes are present, and to replicate the HIV virus binds to the protein CD4 which is most frequently found on T-Helper cells.
• The vacuum environment is needed within an electron microscope so that particles in the air do not deflect the electrons out of the beam alignment.
• In a transmission electron microscope, a beam of electrons passes through a thin section of a specimen, with areas that absorb the electrons appearing darker on the electron micrograph that is produced.
• Mitosis is important for growth as all cells produced are identical so organisms can grow using mitosis.
• The ultrastructure of eukaryotic cells can be obtained by using a microscope.
• Mitosis is important for repair as all cells produced are identical so organisms can replace dead tissues using mitosis.
• A granular jelly-like material called nucleoplasm makes up the bulk of the nucleus.
• Humans are made up of eukaryotic cells.
• The nucleus of a eukaryotic cell contains chromatin and a nucleolus which is the site of ribosome production.
• The inner membrane of mitochondria is folded to form projections called cristae with a matrix on the inside containing all the enzymes needed for respiration.
• The nucleus of a eukaryotic cell is a double membrane called the envelope containing ~3000 nuclear pores that enables molecules to enter and leave.
• The smooth endoplasmic reticulum is a system of membrane-bound sacs that produces and processes lipids.
• The rough endoplasmic reticulum is a series of flattened sacs enclosed by a membrane with ribosomes on the surface.
• Cells of multicellular organisms are organised into tissues, tissues into organs and organs into systems.
• Lysosomes are vesicles containing digestive enzymes bound by a single membrane.
• The Golgi apparatus is a series of fluid-filled, flattened & curved sacs with vesicles surrounding the edges.
• Mitochondria are oval-shaped, bound by a double membrane called the envelope.
• Centrioles are hollow cylinders containing a ring of microtubules arranged at right angles to each other.
• All eukaryotic cells contain a nucleus and membrane-bound organelles.
• The role of mitosis and the cell cycle is to produce identical daughter cells for growth and asexual reproduction.